/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.test.context.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.support.BeanDefinitionReader;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigUtils;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.test.context.MergedContextConfiguration;
import org.springframework.util.StringUtils;

/**
 * Abstract, generic extension of {@link AbstractContextLoader} that loads a
 * {@link GenericApplicationContext}.
 *
 * <ul>
 * <li>If instances of concrete subclasses are invoked via the
 * {@link org.springframework.test.context.ContextLoader ContextLoader} SPI, the
 * context will be loaded from the <em>locations</em> provided to
 * {@link #loadContext(String...)}.</li>
 * <li>If instances of concrete subclasses are invoked via the
 * {@link org.springframework.test.context.SmartContextLoader SmartContextLoader}
 * SPI, the context will be loaded from the {@link MergedContextConfiguration}
 * provided to {@link #loadContext(MergedContextConfiguration)}. In such cases, a
 * {@code SmartContextLoader} will decide whether to load the context from
 * <em>locations</em> or <em>annotated classes</em>.</li>
 * </ul>
 *
 * <p>Concrete subclasses must provide an appropriate implementation of
 * {@link #createBeanDefinitionReader createBeanDefinitionReader()},
 * potentially overriding {@link #loadBeanDefinitions loadBeanDefinitions()}
 * as well.
 *
 * @author Sam Brannen
 * @author Juergen Hoeller
 * @author Phillip Webb
 * @see #loadContext(MergedContextConfiguration)
 * @see #loadContext(String...)
 * @since 2.5
 */
public abstract class AbstractGenericContextLoader extends AbstractContextLoader {

    protected static final Log logger = LogFactory.getLog(AbstractGenericContextLoader.class);


    /**
     * Load a Spring ApplicationContext from the supplied {@link MergedContextConfiguration}.
     *
     * <p>Implementation details:
     *
     * <ul>
     * <li>Calls {@link #validateMergedContextConfiguration(MergedContextConfiguration)}
     * to allow subclasses to validate the supplied configuration before proceeding.</li>
     * <li>Creates a {@link GenericApplicationContext} instance.</li>
     * <li>If the supplied {@code MergedContextConfiguration} references a
     * {@linkplain MergedContextConfiguration#getParent() parent configuration},
     * the corresponding {@link MergedContextConfiguration#getParentApplicationContext()
     * ApplicationContext} will be retrieved and
     * {@linkplain GenericApplicationContext#setParent(ApplicationContext) set as the parent}
     * for the context created by this method.</li>
     * <li>Calls {@link #prepareContext(GenericApplicationContext)} for backwards
     * compatibility with the {@link org.springframework.test.context.ContextLoader
     * ContextLoader} SPI.</li>
     * <li>Calls {@link #prepareContext(ConfigurableApplicationContext, MergedContextConfiguration)}
     * to allow for customizing the context before bean definitions are loaded.</li>
     * <li>Calls {@link #customizeBeanFactory(DefaultListableBeanFactory)} to allow for customizing the
     * context's {@code DefaultListableBeanFactory}.</li>
     * <li>Delegates to {@link #loadBeanDefinitions(GenericApplicationContext, MergedContextConfiguration)}
     * to populate the context from the locations or classes in the supplied
     * {@code MergedContextConfiguration}.</li>
     * <li>Delegates to {@link AnnotationConfigUtils} for
     * {@link AnnotationConfigUtils#registerAnnotationConfigProcessors registering}
     * annotation configuration processors.</li>
     * <li>Calls {@link #customizeContext(GenericApplicationContext)} to allow for customizing the context
     * before it is refreshed.</li>
     * <li>Calls {@link #customizeContext(ConfigurableApplicationContext, MergedContextConfiguration)} to
     * allow for customizing the context before it is refreshed.</li>
     * <li>{@link ConfigurableApplicationContext#refresh Refreshes} the
     * context and registers a JVM shutdown hook for it.</li>
     * </ul>
     *
     * @return a new application context
     * @see org.springframework.test.context.SmartContextLoader#loadContext(MergedContextConfiguration)
     * @see GenericApplicationContext
     * @since 3.1
     */
    @Override
    public final ConfigurableApplicationContext loadContext(MergedContextConfiguration mergedConfig) throws Exception {
        if (logger.isDebugEnabled()) {
            logger.debug(String.format("Loading ApplicationContext for merged context configuration [%s].",
                    mergedConfig));
        }

        validateMergedContextConfiguration(mergedConfig);

        GenericApplicationContext context = new GenericApplicationContext();

        ApplicationContext parent = mergedConfig.getParentApplicationContext();
        if (parent != null) {
            context.setParent(parent);
        }
        prepareContext(context);
        prepareContext(context, mergedConfig);
        customizeBeanFactory(context.getDefaultListableBeanFactory());
        loadBeanDefinitions(context, mergedConfig);
        AnnotationConfigUtils.registerAnnotationConfigProcessors(context);
        customizeContext(context);
        customizeContext(context, mergedConfig);
        context.refresh();
        context.registerShutdownHook();
        return context;
    }

    /**
     * Validate the supplied {@link MergedContextConfiguration} with respect to
     * what this context loader supports.
     * <p>The default implementation is a <em>no-op</em> but can be overridden by
     * subclasses as appropriate.
     *
     * @param mergedConfig the merged configuration to validate
     * @throws IllegalStateException if the supplied configuration is not valid
     *                               for this context loader
     * @since 4.0.4
     */
    protected void validateMergedContextConfiguration(MergedContextConfiguration mergedConfig) {
        // no-op
    }

    /**
     * Load a Spring ApplicationContext from the supplied {@code locations}.
     *
     * <p>Implementation details:
     *
     * <ul>
     * <li>Creates a {@link GenericApplicationContext} instance.</li>
     * <li>Calls {@link #prepareContext(GenericApplicationContext)} to allow for customizing the context
     * before bean definitions are loaded.</li>
     * <li>Calls {@link #customizeBeanFactory(DefaultListableBeanFactory)} to allow for customizing the
     * context's {@code DefaultListableBeanFactory}.</li>
     * <li>Delegates to {@link #createBeanDefinitionReader(GenericApplicationContext)} to create a
     * {@link BeanDefinitionReader} which is then used to populate the context
     * from the specified locations.</li>
     * <li>Delegates to {@link AnnotationConfigUtils} for
     * {@link AnnotationConfigUtils#registerAnnotationConfigProcessors registering}
     * annotation configuration processors.</li>
     * <li>Calls {@link #customizeContext(GenericApplicationContext)} to allow for customizing the context
     * before it is refreshed.</li>
     * <li>{@link ConfigurableApplicationContext#refresh Refreshes} the
     * context and registers a JVM shutdown hook for it.</li>
     * </ul>
     *
     * <p><b>Note</b>: this method does not provide a means to set active bean definition
     * profiles for the loaded context. See {@link #loadContext(MergedContextConfiguration)}
     * and {@link AbstractContextLoader#prepareContext(ConfigurableApplicationContext, MergedContextConfiguration)}
     * for an alternative.
     *
     * @return a new application context
     * @see org.springframework.test.context.ContextLoader#loadContext
     * @see GenericApplicationContext
     * @see #loadContext(MergedContextConfiguration)
     * @since 2.5
     */
    @Override
    public final ConfigurableApplicationContext loadContext(String... locations) throws Exception {
        if (logger.isDebugEnabled()) {
            logger.debug(String.format("Loading ApplicationContext for locations [%s].",
                    StringUtils.arrayToCommaDelimitedString(locations)));
        }
        GenericApplicationContext context = new GenericApplicationContext();
        prepareContext(context);
        customizeBeanFactory(context.getDefaultListableBeanFactory());
        createBeanDefinitionReader(context).loadBeanDefinitions(locations);
        AnnotationConfigUtils.registerAnnotationConfigProcessors(context);
        customizeContext(context);
        context.refresh();
        context.registerShutdownHook();
        return context;
    }

    /**
     * Prepare the {@link GenericApplicationContext} created by this {@code ContextLoader}.
     * Called <i>before</i> bean definitions are read.
     *
     * <p>The default implementation is empty. Can be overridden in subclasses to
     * customize {@code GenericApplicationContext}'s standard settings.
     *
     * @param context the context that should be prepared
     * @see #loadContext(MergedContextConfiguration)
     * @see #loadContext(String...)
     * @see GenericApplicationContext#setAllowBeanDefinitionOverriding
     * @see GenericApplicationContext#setResourceLoader
     * @see GenericApplicationContext#setId
     * @see #prepareContext(ConfigurableApplicationContext, MergedContextConfiguration)
     * @since 2.5
     */
    protected void prepareContext(GenericApplicationContext context) {
    }

    /**
     * Customize the internal bean factory of the ApplicationContext created by
     * this {@code ContextLoader}.
     *
     * <p>The default implementation is empty but can be overridden in subclasses
     * to customize {@code DefaultListableBeanFactory}'s standard settings.
     *
     * @param beanFactory the bean factory created by this {@code ContextLoader}
     * @see #loadContext(MergedContextConfiguration)
     * @see #loadContext(String...)
     * @see DefaultListableBeanFactory#setAllowBeanDefinitionOverriding
     * @see DefaultListableBeanFactory#setAllowEagerClassLoading
     * @see DefaultListableBeanFactory#setAllowCircularReferences
     * @see DefaultListableBeanFactory#setAllowRawInjectionDespiteWrapping
     * @since 2.5
     */
    protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
    }

    /**
     * Load bean definitions into the supplied {@link GenericApplicationContext context}
     * from the locations or classes in the supplied {@code MergedContextConfiguration}.
     *
     * <p>The default implementation delegates to the {@link BeanDefinitionReader}
     * returned by {@link #createBeanDefinitionReader(GenericApplicationContext)} to
     * {@link BeanDefinitionReader#loadBeanDefinitions(String) load} the
     * bean definitions.
     *
     * <p>Subclasses must provide an appropriate implementation of
     * {@link #createBeanDefinitionReader(GenericApplicationContext)}. Alternatively subclasses
     * may provide a <em>no-op</em> implementation of {@code createBeanDefinitionReader()}
     * and override this method to provide a custom strategy for loading or
     * registering bean definitions.
     *
     * @param context      the context into which the bean definitions should be loaded
     * @param mergedConfig the merged context configuration
     * @see #loadContext(MergedContextConfiguration)
     * @since 3.1
     */
    protected void loadBeanDefinitions(GenericApplicationContext context, MergedContextConfiguration mergedConfig) {
        createBeanDefinitionReader(context).loadBeanDefinitions(mergedConfig.getLocations());
    }

    /**
     * Factory method for creating a new {@link BeanDefinitionReader} for loading
     * bean definitions into the supplied {@link GenericApplicationContext context}.
     *
     * @param context the context for which the {@code BeanDefinitionReader}
     *                should be created
     * @return a {@code BeanDefinitionReader} for the supplied context
     * @see #loadContext(String...)
     * @see #loadBeanDefinitions
     * @see BeanDefinitionReader
     * @since 2.5
     */
    protected abstract BeanDefinitionReader createBeanDefinitionReader(GenericApplicationContext context);

    /**
     * Customize the {@link GenericApplicationContext} created by this
     * {@code ContextLoader} <i>after</i> bean definitions have been
     * loaded into the context but <i>before</i> the context is refreshed.
     *
     * <p>The default implementation is empty but can be overridden in subclasses
     * to customize the application context.
     *
     * @param context the newly created application context
     * @see #loadContext(MergedContextConfiguration)
     * @see #loadContext(String...)
     * @see #customizeContext(ConfigurableApplicationContext, MergedContextConfiguration)
     * @since 2.5
     */
    protected void customizeContext(GenericApplicationContext context) {
    }

}
